Electrophysiological studies in patients with seropositive/seronegative myasthenia gravis

Zahra Vahabi; Ferdos Nazari; Farzad Fatehi; Valiolah Bayegi; Zahra Saffarian; Fatemeh Saffarian; Shahriar Nafissi

doi:10.18502/cjn.v20i3.7686

Zahra Vahabi Department of Geriatric Medicine, Ziaeian Hospital, Tehran University of Medical Sciences, Tehran, Iran
Ferdos Nazari Department of Neurology, Shariati Hospital, Neuromuscular Research Center, Tehran University of Medical Sciences, Tehran, Iran
Farzad Fatehi Department of Neurology, Shariati Hospital, Neuromuscular Research Center, Tehran University of Medical Sciences, Tehran, Iran
Valiolah Bayegi Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
Zahra Saffarian Department of Dermatology, School of Medicine, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran
Fatemeh Saffarian Department of Cardiology, School of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran
Shahriar Nafissi Department of Neurology, Shariati Hospital, Neuromuscular Research Center, Tehran University of Medical Sciences, Tehran, Iran

DOI: https://doi.org/10.18502/cjn.v20i3.7686

Keywords: Electrophysiology; Myasthenia Gravis; Patients

Abstract

Background: Myasthenia gravis (MG) affects the neuromuscular transmission, causing fluctuating muscle weakness and fatigue. This study is carried out with the aim to study the electrophysiologic findings of different subtypes of MG referred to our center in Tehran, Iran.

Methods: All patients with MG presenting to neurology department of Shariati Hospital, Tehran University of Medical Sciences were enrolled. Clinically, patients with MG were categorized as ocular vs. generalized. The acetylcholine receptor (Ach-R) and muscle-specific receptor tyrosine kinase (anti-MuSK) antibodies were performed. Repetitive Nerve Stimulation (RNS) was performed using the standard method, with supramaximal stimulation of muscles at the 3 Hz frequency by surface electrode at rest. Abductor pollicis brevis (APB) (median nerve), anconeus (radial nerve), trapezius (accessory nerve), and nasalis (facial nerve) muscles were studied in all patients. Single fiber electromyography (SFEMG) was performed by standard method.

Results: 196 seropositive patients with MG were included in the study. In electrophysiological studies, RNS was performed for 146 patients of Ach-R-Ab positive MG, with positive results in 110 patients. In addition, SFEMG was conducted for 8 patients with negative RNS, which resulted in 7 positive tests.